Dyslipidemia generally refers to high blood cholesterol levels and is asymptomatic. However, dyslipidemia is a very serious condition, because it causes angina pectoris, myocardial infarction and arteriosclerosis. Statins, drugs that are commonly used to treat hyperlipidemia, exhibit therapeutic effects mainly by lowering LDL-C, but their effects on the prevention of cardiovascular diseases are still very insufficient. A recent study reported that not only lowering low-density lipoprotein cholesterol (LDL-C) levels, but also increasing high-density lipoprotein cholesterol (HDL-C) levels is very effective in preventing cardiovascular diseases (Goldbourt et al., 1997, 17, 107-113). Among drugs that are used to increase HDL-C levels, the most effective drug is Niacin. However, this drug needs to be taken in relatively large doses and causes side effects such as facial flushing (Taylor et al., Circulation, 2004, 110, 3512-3517).
Meanwhile, cholesterol ester transfer protein (CETP) is a protein that participates in reverse cholesterol transport (the transport of cholesterol from peripheral tissue to the liver). When CETP is inhibited, HDL-C levels can be effectively increased, thus preventing cardiovascular diseases. Accordingly, the development of compounds capable of inhibiting CETP activity is very important (Barter et al., Arterioscler Thromb Vase Biol, 2003, 23, 160-167).
CETP inhibitors developed to date include Torcetrapib (International Patent Publication No. WO 02/088085), Anacetrapib (International Patent Publication No. WO 2006/014357) and Evacetrapib (US Patent Publication No. 2010/0331309), which are structurally similar to each other. In addition, Dalcetrapib (International Patent Publication No. WO 98/35937), a benzenethiol derivative, is known as a CETP inhibitor.
However, among these CETP inhibitors, Torcetrapib (Pfizer) causes an increase in blood pressure and an increase in mortality rate, and thus was stopped phase III clinical trial. It was reported that such side effects occur because Torcetrapib increases the levels of hormones, such as aldosterone and corticosterone, associated with an elevation in blood pressure, and increases the thickness of the vascular wall to cause inflammation, thus increasing mortality rate (Forrest et al, British Journal of Pharmacology, 2008, 1-9).
The other CETP inhibitor Dalcetrapib (Roche) was also stopped in phase III clinical trial, and it is known that Dalcetrapib does not have the side effects of Torcetrapib, but has insufficient effects (Alyse S Goldberg et al, Drug Design Development and Therapy, 2012, 6, 251-259).
Recently, the results of phase III DEFINE trial (Determining the Efficacy and Tolerability of CETP Inhibition with Anacetrapib)) for Anacetrapib (Merck) indicated that, in the case of patients administered with Anacetrapib, the HDL-c level increased by 138% and the LDL-c level decreased by 40% (Philip Barter et al, The New England Journal of Medicine, 2010, 363, 2406-2415). Based on such results, Merck has performed clinical trials on about 30,000 persons in order to examine whether administration of Anacetrapib ameliorate cardiovascular diseases (ClinicalTrials.gov, NCT01252953).
In addition, the results of phase II clinical trials for Evacetrapib (Lilly) showed that Evacetrapib increases HDL-c levels in a dose-dependent manner and does not cause side effects such blood pressure elevation. Recently, Evacetrapib entered phase III clinical trials on 10,000 persons (ClinicalTrials.gov, NCT01687998).
Efforts have been made to develop novel CETP inhibitors having more advantages over CETP inhibitors developed to date or CETP inhibitors being developed. Such advantages may include excellent efficacy, reduced off-target effects, increased bioavailability, reduced food effects, etc.